nubus: generate bus error when attempting to access empty slots
According to "Designing Cards and Drivers for the Macintosh Family" any attempt
to access an unimplemented address location on Nubus generates a bus error. MacOS
uses a custom bus error handler to detect empty Nubus slots, and with the current
implementation assumes that all slots are occupied as the Nubus transactions
never fail.
Switch nubus_slot_ops and nubus_super_slot_ops over to use {read,write}_with_attrs
and hard-code them to return MEMTX_DECODE_ERROR so that unoccupied Nubus slots
will generate the expected bus error.
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20210924073808.1041-9-mark.cave-ayland@ilande.co.uk>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
diff --git a/hw/nubus/nubus-bus.c b/hw/nubus/nubus-bus.c
index a9fb6de..215fdb6 100644
--- a/hw/nubus/nubus-bus.c
+++ b/hw/nubus/nubus-bus.c
@@ -28,23 +28,23 @@
return NUBUS_BUS(object_resolve_path_type("", TYPE_NUBUS_BUS, NULL));
}
-static void nubus_slot_write(void *opaque, hwaddr addr, uint64_t val,
- unsigned int size)
+static MemTxResult nubus_slot_write(void *opaque, hwaddr addr, uint64_t val,
+ unsigned size, MemTxAttrs attrs)
{
- /* read only */
trace_nubus_slot_write(addr, val, size);
+ return MEMTX_DECODE_ERROR;
}
-static uint64_t nubus_slot_read(void *opaque, hwaddr addr,
- unsigned int size)
+static MemTxResult nubus_slot_read(void *opaque, hwaddr addr, uint64_t *data,
+ unsigned size, MemTxAttrs attrs)
{
trace_nubus_slot_read(addr, size);
- return 0;
+ return MEMTX_DECODE_ERROR;
}
static const MemoryRegionOps nubus_slot_ops = {
- .read = nubus_slot_read,
- .write = nubus_slot_write,
+ .read_with_attrs = nubus_slot_read,
+ .write_with_attrs = nubus_slot_write,
.endianness = DEVICE_BIG_ENDIAN,
.valid = {
.min_access_size = 1,
@@ -52,23 +52,25 @@
},
};
-static void nubus_super_slot_write(void *opaque, hwaddr addr, uint64_t val,
- unsigned int size)
+static MemTxResult nubus_super_slot_write(void *opaque, hwaddr addr,
+ uint64_t val, unsigned size,
+ MemTxAttrs attrs)
{
- /* read only */
trace_nubus_super_slot_write(addr, val, size);
+ return MEMTX_DECODE_ERROR;
}
-static uint64_t nubus_super_slot_read(void *opaque, hwaddr addr,
- unsigned int size)
+static MemTxResult nubus_super_slot_read(void *opaque, hwaddr addr,
+ uint64_t *data, unsigned size,
+ MemTxAttrs attrs)
{
trace_nubus_super_slot_read(addr, size);
- return 0;
+ return MEMTX_DECODE_ERROR;
}
static const MemoryRegionOps nubus_super_slot_ops = {
- .read = nubus_super_slot_read,
- .write = nubus_super_slot_write,
+ .read_with_attrs = nubus_super_slot_read,
+ .write_with_attrs = nubus_super_slot_write,
.endianness = DEVICE_BIG_ENDIAN,
.valid = {
.min_access_size = 1,
